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Surgical Basics > Wound Healing > Flashcards

Wound Healing Flashcards

1
Q

What is different about the skin blood supply in cats and dogs vs humans?

A

The presence of direct cutaneous vessels as opposed to perforating musculocutaneous vessels

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2
Q

What does The presence of direct cutaneous vessels in cats and dogs allow?

A

Elevate and mobilise large skin flaps.

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3
Q

What is key to preserve to create a successful skin flap?

A

Preservation of the deep dermal plexus

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4
Q

In full thickness skin wounds, what is the source of epithelial cells which cover the wound?

A

stratum germinativum

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5
Q

What are the epidermic hair bearing areas?

A

stratum corneum and the stratum germinativum

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6
Q

The hypodermis is below the dermis.
What does this contain. How does it differ in the head, neck and trunk.

A

Adipose tissue and loose connective tissue

A thin panniculus muscle is present in the head,neck and trunk

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7
Q

How is the skin supplied with blood?

A

Direct cutaneous vessels which run parallel to the skin within the hypodermis.

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8
Q

What do the terminal branches of the direct cutaneous vessels form?

A

A rich capillary plexus - deep dermal (/ subdermal) plexus

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9
Q

In areas of skin with a panniculus muscle, where does the subdermal plexus run?

A

Above and below panniculus muscle

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10
Q

What is the main collagen type in skin?

A

Type 1

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11
Q

The skin is viscoelastic and exhibits hysteresis, what is this?

A

The stress-strain curve is non-linear.

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12
Q

What is mechanical creep? What causes this in skin?

A

The skin undergoes time-dependent plastic strain while under constant stress, meaning it is stretched beyond its inherent extensibility.

Thought to be due to the realignment of collagen fibres.

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13
Q

What is stress relaxation? What is it thought to be due to?

A

a decrease in the level of stress under the same amount of strain.

The breakage of collagen fibres and permanent plastic strain. Breakage of elastin fibres leads to a loss of the skin’s elastic recoil under constant strain.

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14
Q

When does first intention healing occur?

A

when the wound edges are sutured.

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15
Q

When does second intention healing occur?

A

When there is tissue loss and the wound edges cannot be apposed. This type of healing is also referred to as open-wound healing.

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16
Q

When does third intention healing occur?

A

When there is a delay in closing the wound, typically because of concerns about infection or devitalisation.

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17
Q

What chemical is release by cells in wounds?

A

Cytokines

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18
Q

What functions do cytokines have? (3)

A
  • Autocrine
  • Paracrine
  • Direct the synthesis of compounds for wound healing
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19
Q

What are the 3 phases of wound healing?

A
  • Inflammatory
  • Proliferative
  • Maturation and remodelling
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20
Q

What are the key steps of the inflammatory phase? (3)

A
  • Haemostasis
  • Recruitment of inflammatory cells into the wound
  • Debridement.
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21
Q

Inflammatory phase:
What does a blood clot contain? and what is it the basis for?

A

Fibrin and fibronectin
Basis of the provisional extracellular matrix

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22
Q

Inflammatory phase:
What does the provisional extracellular matric allow?

A

Cells t migrate into the wound - ats as a scaffold.

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23
Q

Inflammatory phase:
What do platelets within the clot release and results in (3)?

A

Vasoactive compounds
- vasodilation, cytokines (chemotactic for WBC)

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24
Q

Inflammatory phase:
How do WBC leave circulation and enter wound? (2)

A

Margination and diapedesis

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25
Q

Inflammatory phase:
What is the first inflammatory cell at the wound?

A

Neitrophil

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26
Q

Inflammtory phase:
What do neutrophils release?
What do neutrophils have a role in? (3)

A
  • Proteinases debride necrotic tissue
  • bacterial killing (phagocytosus)
  • Production of free radicals
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27
Q

What is free radical production reliant on?

A

Oxygen (hence need for perfusion)

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27
Q

Inflammatory phase;
What happens to neutrophils after a few days?

A

Apoptosis

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28
Q

Inflammatoty phase:
What cell follows neutrophils?

A

Monocytes

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29
Q

Inflammatory phase:
What is the role of monocytes? (3)

A
  • Phagocytosis
    -Wound debridement, - Produce cytokines which are chemotactic for proliferative stage
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30
Q

What is the primary cell in wound within 48-96 hours?

A

monocytes

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31
Q

… are responsible for activation of the clotting cascade, formation of the provisional extracellular matrix and release of chemotactic cytokines.

A

Platelets

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32
Q

… are responsible for debridement of necrotic tissue and bacterial killing.

A

Neutrophils

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33
Q

.. are the dominant cell in the wound by 48-96 hours and have a role in wound debridement and the recruitment of cells involved in the proliferative phases of wound healing.

A

Macrophages

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34
Q

What days of wound healing is the proliferative phase?

A

5-20

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35
Q

What is the hallmark of the proliferative phase?

A

Granulation tissue

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36
Q

What does granulation tissue contain? (4)

A

Macrophages
Fibroblasts
Capillary buds
A ground substance.

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37
Q

What 4 processes are involved in proliferative stage?

A

Angiogeneis
Fibreoplasia
Epithelization
Wound contraction

38
Q

What does angiogenesis develop in result of? (2)

A

Growth factors
Wound factors e.g. Low O2 tension

39
Q

Proliferative phase:
What is fibroplasia?

A

Fibroplasia is the proliferation of fibroblasts at the margin of the wound and their migration across the fibrin scaffold of the wound bed.

40
Q

Proliferative phase:
What do fibroblasts produce to aid migration? (2)

A

Proteolytic enzymes:
Plasminogen activator Matrix metalloproteinases (MMPs)

41
Q

Proliferative phase:
What do fibroblasts initially produce to form a loose extracellular matrix?

A

Fibronectin

42
Q

Proliferative phase:
Following the production of fibronectin, what is produced following this? (round 4-5 days after wounding)

A

Collagen type III

43
Q

Why is the production of collagen type III a critical period of wound healing?

A

Wound gains tensile strength

44
Q

How long does the fibroblastic phase of proliferative phase last?

A

2-4 weeks

45
Q

After fibroplasia phase (proliferative phase); the fibroblasts and capillaries decrease - what is then complete?

A

Net collagen synthesis

46
Q

What is epithelialisation?

A

Epithelialisation is the restoration of an epithelial surface.

47
Q

When does epithelialisation begin?

A

1-2 days

48
Q

Epithelialisation (proliferative):
What is the source of epithelial cells:
A) full thickness wounds?
B) Partial thickness wounds?

A

A) Wound edges
B) Dermal adnexa

49
Q

In a sutured wound, how long does it take for a small dermal gap to bridge? (Epithelialisation)

A

48 hours

50
Q

Wound contractions (proliferation phase):
What happens to the fibroblasts?

A

Fibroblasts within the wound develop smooth muscle properties and become myofibroblasts.

51
Q

When does wound contraction start?

A

Days 5-8

52
Q

When does wound contraction decline?

A

6 weeks

53
Q

After how long does The wound does not support further epithelialisation or contraction and becomes a chronic granulating wound

A

2-4 weeks

54
Q

… is the formation of a new capillary network across the wound.

A

Angiogensis

55
Q

… is the proliferation of fibroblasts and the production of type III collagen, which provides early wound strength.

A

Fibroplasia

56
Q

… is the mobilisation and migration of epithelial cells across the wound to restore an epithelial surface.

A

Epithelialisation

57
Q

… is the centripetal movement of the skin edges to shrink and close the wound.

A

Contraction

58
Q

What is the main aim of the matruation and remodelling phase?

A

Strengthening collagen
Collagen type III to type I

59
Q

Maturation and remodelling phase - Collagen degradation by collagenase enzymes is balanced by?

A

Tissue inhibitors of metalloproteinases (TIMPs)

60
Q

Net collagen synthesis:
A) When is it complete after injury?
B) How long does maturation continue for?

A

A) 4-5 weeks
B) 12-18 weeks

61
Q

What is the wound strength of skin ay 10-14 days?

A

5-10%

61
Q

What is the wound strength at 3months?

A

80%

61
Q

What is the wound strength at 3-4 weeks?

A

25%

62
Q

What is pseudohealing?

A

Sutured wounds appear healed once epithelialisation is complete. However, they may not yet have gained enough tensile strength to guarantee apposition once skin sutures are removed. = dehiscence

63
Q

What is the difference between dog and cat wound healing at 7 days?

A

Feline sutured wounds have been shown to be slower to heal, being only 50% as strong

64
Q

Why is a cat wound slower to heal?

A

Lower cutaneous perfusion in the first week after surgery, followed by a more rapid gain during the second week

65
Q

What is different with cat granulation vs dogs?

A

Cats produce less granulation tissue than dogs, with a peripheral rather than central distribution.

66
Q

What was the difference in wound area by contraction/epithelialisation over 21 days?

A

Reduction greater in dogs

67
Q

How do dog wounds close?

A

Central pull and epithelization

67
Q

How dog cats wounds close?

A

Contraction of wound edges

67
Q

In both cats and dogs, it is important to preserve ……. in second intention healing, but less so in first intention healing.

A

Subcutaenous tissue

67
Q

What are the layers of the GI tract? (4)

A

Mucosa
Submucosa
Musularis propria
Serosa

68
Q

What collagen does submucosa of GIT contain?

A

I
II
V

69
Q

What layer provides tensile strength to GIT

A

Submucosa

70
Q

During GIT closure, why must we not over tighten sutures? (we should anticipate)

A

Anticipate oedema which occurs in the mucosa and submucosa layer

71
Q

During GI closure, what forms rapidly at the outer serosal layer providing the watertight seal?

A

Fibrin seal

72
Q

During GIT healing, what produces collagen in the proliferative phase? (2)

A

Fibroblasts
Smooth muscle cells

73
Q

When is wound breakdown of GIT most likely to happen?

A

days 2-5

74
Q

In terms of healing phases, why is GIT dehiscence most likely to happen day 2-5?

A

Collagen lysis during the inflammatory or lag phase results in a net loss of wound strength.

75
Q

After day 2-5 of GI wound - what is gained day 2-5?

A

tensile strength

76
Q

What factors affect GIT wound healing? (3)

A
  • shear stress due to increased intraluminal pressure during peristalsis and transport of ingesta;
  • the presence of aerobic and anaerobic bacteria;
  • adequate oxygen delivery.
77
Q

How long does re-epithelialisation take following injury of uroepithelial cells?

A

2-4 days (there is a rapid increase in mitotic activity)

78
Q

How long does it take for collagen synthesis to reach its peak in the urinary bladder post surgery?

A

5days

79
Q

How long does it take for the urinary bladder to regain 100% of its unwounded strength?

A

21 days

80
Q

After surgery - how long does it take for the urinary bladder collagen synthesis to return to normal?

A

70 days

81
Q

Why is the fascial healing inflammatory phase prolonged?

A

This is thought to be due to the longer distances cells must migrate to reach the relatively avascular and acellular wound edges.

82
Q

How long do fascial wounds have no inherent strength for?

A

7 days

83
Q

What does fascial wound strength depend on?

A

Suture material

84
Q

What is the wound strength of a fascial wound after 3-4 weeks?

A

50%

85
Q

Fascial wound:
Where should sutures be placed in relation to wound edges?

A

3mm

86
Q

Why should sutures avoid 3mm from edges of fascia wounds?

A

There is a zone of collagenolysis and matrix degradation at the wound edges.

87
Q

What systematic factors DELAY wound healing? (4)

A
  • Poor immune function
  • Chemotherapy
  • Radiotherapy
  • Age
88
Q

Name local factors which impact wound healing (5)

A
  • Wound perfusion
  • Necrotic tissue/Foreign material
  • Haematoma/seroma
  • Bacteria contamination
  • 1ry wound closure if preferred to 2ry

Surgical Basics (10 decks)

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